Life activities in space environment

This review summarized biological life activities in space environment for investigating which many experiments had been done in spacecraft's. The space is characterized by a good view, high vacuum, scarce gravity and cosmic ray of which exposure dose in the craft at 4,000 km height is around 1,000 times higher than the dose on the ground. In humans, reductions of bone content, muscle strength, immune function are known as well as space intoxication and eye-flash. Authors carried out 17 experiments in American and Russian space stations from 1992. The experiments concerned DNA breakage by cosmic ray where they first visualized the DNA damage by the ray with autoradiographic method with [3H]dATP in HMV1 cells; cell differentiation and morphogenesis in the space with the use of radio-sensitive cellular slime mold of γs13 strain; influences of the scarce gravity on the repair of broken artificially prepared double-strand DNA and on the induced-mutation in E. coli and yeast; and stress proteins which were shown to be accumulated in the space. The space experiments are concluded to be useful for radiation biology further in future. (K.H.)